A gas turbine includes, for example, a compressor, a combustor, and a turbine. The compressor compresses air taken in through an air intake to produce compressed air that is at high temperature and high pressure. In the combustor, the compressed air is mixed with fuel, and the mixture is burned to produce combustion gas at high temperature and high pressure. The combustion gas is provided to the turbine to produce rotative power, thereby driving a generator connected to the turbine. The turbine is so configured that a plurality of stator vanes and a plurality of rotor blades are alternately arranged in a casing thereof. The combustion gas drives the rotor blades, thereby rotatively driving an output shaft to which the generator is connected. After driving the turbine, the combustion gas is converted into static pressure by a diffuser of an exhaust casing, and then, is released into the atmosphere.
FIG. 14 is a schematic view of a conventional gas turbine combustor. In a conventional gas turbine combustor, a casing is, as shown in FIG. 14, configured so that a combustor inner tube 002 is supported in the interior of a combustor outer casing 001 and that a combustor transition piece 003 is connected to a tip end portion of the combustor inner tube 002. An air passage 004 is formed between the combustor outer casing 001 and the combustor inner tube 002. In the interior of the combustor inner tube 002, a pilot nozzle 005 is arranged in the center thereof, a plurality of main fuel nozzles 006 is arranged on the inner circumference of the combustor inner tube 001 along the circumferential direction thereof, and a main burner 007 is arranged around the pilot nozzle 005 so that a tip end portion of each main fuel nozzle 006 communicates with the main burner 007. A plurality of top hat nozzles 008 is arranged on the inner circumference of the combustor outer casing 001 along the circumferential direction thereof, and a fuel passage 009 is connected to each top hat nozzle 008.
A pilot fuel line 010 is connected to the pilot nozzle 005, a main fuel line 011 is connected to the main fuel nozzles 006, and a top hat fuel line 012 is connected to the top hat nozzles 008.
Thus, airflow of the compressed air compressed by the compressor that is at high temperature and high pressure flows into the air passage 004 of the gas turbine combustor, and then, is mixed with fuel injected by the top hat nozzles 008. The air fuel mixture flows into the interior of the combustor inner tube 002. In the interior of the combustor inner tube 002, the main burner 007 mixes the air fuel mixture and fuel injected by the main fuel nozzles 006 with each other to produce premixed gas, and then, swirl flow of the premixed gas flows into the interior of the transition piece 003. The air fuel mixture is mixed with fuel injected by the pilot nozzle 005. The mixture thus produced is ignited by a pilot flame (not shown) and is burned to produce combustion gas. The combustion gas is ejected to the interior of the transition piece 003. Some of the combustion gas is ejected into the interior of the transition piece 003 so as to be diffused peripherally accompanying flame. Consequently, the combustion gas is ignited by the premixed gas that flows to the interior of the transition piece 003 from the main fuel nozzle 006, and is burned. Thus, because of diffused flame produced by pilot fuel injected by the pilot nozzle 005, flame is held to stably burn dilute premixed fuel injected by the main fuel nozzles 006.
Such a gas turbine is described, for example, in Patent Documents 1 and 2.    Patent Document 1: Japanese Patent Application Laid-open No. 2001-141243    Patent Document 2: Japanese Patent Application Laid-open No. 2000-171038